There exist EGR apparatuses for circulating a part of an exhaust gas of an internal combustion engine as the EGR gas. With the supply of the EGR gas together with an air-fuel mixture or fresh air to the combustion chamber, decreasing of NOx in the exhaust gas and improving fuel consumption are intended. A technology is known in which the EGR gas with the air-fuel mixture or fresh air is stratified (layered) in the combustion chamber in order to increase the quantity of the EGR gas supplied to the internal combustion engine.
In Patent Document 1, timings of opening and closing of two intake valves are staggered from each other by an opening and closing property changing unit, thereby to cause the EGR gas to flow first into the combustion chamber from an intake port having a swirl control valve, and, thereafter, to cause fresh air to flow into the combustion chamber from the other intake port. Whereby in the combustion chamber, stratification of the EGR gas and fresh air is achieved in which the layer of the EGR gas is a lower layer and the layer of fresh air is an upper layer.